The proposed studies are designed to elucidate the cause for unconjugated hyperbilirubinemia in various liver disorders in man. The hepatic factors involved in the rise of unconjugated serum bilirubin will be studies directly. The pathogenetic significance of the intracytoplasmic bilirubin carrier proteins, bilirubin glucuronidaton process, and bilirubin deglucuronidation process will be assessed in both congenital and acquired conditions associated wth unconjugate hyprbilirubinemia in new born and adult subjects. This study will provide information regarding the effect of phenobarbital, alcohol, caloric intake, dietary components, exercise, and other factors on hepatic bilirubin transport in patients with Gilbert's syndrome. The effect of microsomal enzyme inducers on the activity of UDP-glucuronyl transferase will be studies, which may provide a rational basis for the treatment of severe unconjugated hyperbilirubinemia in the newborn. Elucidation ofthe processes of hepatic bilirubin transport, may allow for a better understanding of the mechanisms involved in the hepatic biotransformation of organic anions, in general.